The blast has left 40 others injured.
The blast occurred at a time when Balochistan Bar Association President Bilal Kasi's body was brought to the hospital.
He was earlier in the day shot by attackers.
Police was quoted as saying by Geo News that unknown men opened fire after the blast.
According to reports, the blast occurred close to the emergency department of the hospital.
No group has claimed responsibility for the attack so far.
Pakistan PM Nawaz Sharif condemned the attack.
"No one will be allowed to disrupt the peace of the province," he was quoted as saying by Geo News.